In addition to the official course textbook (written by me), I have
made some other notes available for your reference. The main
secondary reference is
Formal Systems and Logic in Computing Science
by W.W. Armstrong, F.J. Pelletier, R.A. Reckhow, & P. Rudnicki.
aka "The Alberta Notes", especially these chapters:
Alberta Notes, Chp 3
Alberta Notes, Chp 4
In the Alberta Notes there are some minor differences in the actual rules used, particularly for negation. But the general strategy for constructing proofs is similar to ours, so I hope these notes may be helpful to you.
I have linked the relevant sections of the Alberta Notes to the units where they are relevant, so you know when they are useful.
In Unit 2 I have also given you some notes from a course given at the University of Ottawa. The notational conventions for that course are slightly different from those used in this course: the main difference is the marking of hypotheses in formal proofs: at U of O they explicitly mark them, whereas we do not (the special underlining being sufficient to indicate them).
If those differences give you any problems, please ask me about it. I think the similarities are more significant, and some students have found the extra written explanations helpful.
There are other readings, as linked on the course webpage. You should also look at the "Entertainments" section, where further material is suggested.